In secondary or tertiary oil recovery operations, recovery of oil is maximized if the driven fluid is permitted to build up in a wide bank in front of the driving fluid which moves uniformly toward a producing well. To keep this bank of oil intact, and moving toward a producing well, a substantially uniform permeability must exist throughout the strata. If this uniform permeability does not exist, and it generally does not, the flooding will seek the areas of high permeability, and channeling occurs with the appearance of excess driving fluid at the producing well. Moreover, as the more permeable strata are depleted, the driving fluid has a tendency to follow these channels and further increase water production as reflected in an increased water/oil ratio to the point that the process becomes economically undesirable.
It is known in the art that more uniform flood fronts can be obtained in formations of nonuniform permeability by control or permeability correction of the more permeable strata of the formation. A number of methods for reducing the permeability of these permeable strata have been proposed, including the injection of plugging materials into these strata which at least partially plug the permeable zones so as to achieve more uniform permeability. Some of these methods of permeability correction accomplish the plugging step by the in situ formation of plugging material in the formation by the injection of one or more reactant substances which chemically react to form a solid residue. These reactant substances include various hydraulic cements, precipitate-forming materials, and monomers or prepolymers which are polymerizable under formation conditions. Unfortunately, however, these plugging materials can also plug less permeable zones. Particularly with the polymerizable materials which may be relatively fluid when injected, the situation can even be made worse by completely shutting off the already less permeable zones.